Google AdSense Back To Square Arrows?

When Google introduced the arrows to the AdSense ads, they came with a colored square background button with an arrow overlaid on the square. Then a year ago, Google went from the square background to a circle background look for the AdSense ads.

Here is the before and after back then:

Now Google seems to be testing the square arrow blocks again. Here is a picture from a publisher in a WebmasterWorld thread:

It is not unusual for Google to bounce around with ad formats in order to change up the ad styles enough to keep the click through rate somewhat up.